This invention relates to apparatus and methods for separating volatile analytes from gaseous mixtures, especially from mixtures containing potentially interfering compounds, and measuring the concentrations of the analytes.
Gas chromatography is widely used to fractionate gaseous mixtures into a stream of purer components eluting at different time intervals, with the most volatile components or those having the lowest molecular weights usually eluting first and the least volatile components (with heaviest molecular weights) eluting after much longer times. Such fractionation may be practical when the elution times are not excessive, e.g., of the order of 10 minutes or less. However, when interferences (i.e., interfering compounds) may be present that take longer times to elute, then erroneous analytical results may be obtained if the duration of an analytical cycle is shorter than the elution time of the least volatile (or "heaviest") interference.
It is a purpose of our invention to provide means for separating volatile components from a gaseous mixture within relatively brief spans of time.
It is another object of our invention to permit accurate measurements of the concentrations of these volatile components without introduction of errors due to less volatile ("heavier") interferences.
It is a further object of this invention to provide cost-effective means for selectively monitoring the concentration of volatile analytes in gaseous mixtures.
It is a particular object of our invention to provide improved means for monitoring carbon monoxide, methanol, methylene chloride, and formaldehyde in the presence of potential interferences.
It is still a further object of our invention to improve the reliability of gas chromatographic analyses involving volatile analytes, especially with the use of portable gas chromatographs.
It is yet another object of our invention to improve the speed and selectivity of chromatographic analyses.
Yet another object of our invention is to provide a convenient and simple separation method that can be implemented for a variety of analytes and with various detection means.